Ok... I have a 79 F250 Camper edition with 460. The PO had an electric fuel pump installed and it runs fine with that as long as the truck runs every day or other day. From my research, they had it installed incorrectly as it went from tank to EFP to MFP to carb and did not bypass MFP. There was no fuel filter installed either. I removed the EFP and put in a fuel filter and truck runs great (If I start it every day or two.) I left town for a week and cannot get it to kick over unless I pour gas in the carb. I am leaning towards a MFP issue but before I replace this, I am wondering if I am barking up the wrong tree. Would a bad fuel pump work (with the carb infusion of gas?) It seems as though it is loosing its prime and I can't figure out how to test the pump. Is there a better brand of MFP to get?

TIA

 

I suggest buying one of those clickty clack electric pumps and put gas in a five gallon jug and puts the gas through each major part of the system and run the truck itself on it and bypass the fuel pump.

 

The carbs on our old school trucks are vented to atmosphere. That means the fuel in the bowl will evaporate if left too long. I have to crank mine for a minute or 2 if it's sat for long, just make sure to let the starter cool down every now and then by only cranking for 15 to 20 seconds at a time.

Thinking about it, this probably led to many a flooded engine. Not realizing that there is no fuel in the bowl so rabid pumping of the pedal while cranking which could flood it via the accelerator pump before the idle circuit gets a chance to work it's magic.

There are only 2 ways you can make it start every time reliably that I can think of. Install an electric pump or start it every other day.

Michael

 

Thanks for the replies... so to get it straight, just let the engine crank without touching the pedal? Also, since this truck has two tanks, the p.o. has locking gas caps and I think they are not vented. Do I need vented on this system or not? Also, if I do go back to the electric pump, am I correct in that it shouldn't be plumbed to the MFP in line after the EFP?
The reason I am thinking the MFP is going out is because when it sat for a while in the other configuration (EFP to MFP to carb) I had the same hard start situation

 

Whether you touch the pedal partly depends on whether you have a manual or automatic choke and how in tune you are with how the truck starts.

With an automatic choke, when you push the pedal down fully without cranking, you set the choke and the high idle cam. Fiddling with the pedal while cranking can knock the high idle cam back down so that you lose the higher idle speed needed to keep it running. So in this case, I'd not touch the pedal once the cam is set but keep cranking off and on until it starts.

With my manual choke, I have to guess where the right idle speed and choke close off is so I tend to fiddle with the pedal as I can feel it's height change with the choke ****. Once that's set, I tend to crank with only an occasional light tap on the pedal to see if it wants to catch. Once it starts to catch, I leave the pedal alone unless I've guessed the choke wrong. When it's warmer out and it's been started in the last day or 2, I just crank it with out choke or pedal then feather the pedal as needed to get it over the hump.

I do not know if you can push fuel through a mechanical pump as it does have check valves so if I were to run an electric, I'd bypass the mechanical pump completely and install a filter on it's inlet even if there is one at the carb already.

Michael

 

Thanks Lasermike.... That makes sense. I think I have been fiddling with he pedal too much while cranking and kicking off the high idle. I have the auto choke and not a manual I looked at the choke plate and once you hit the pedal once after cranking a bit, the plate opens up and I believe I lose benefit of the choke. I think I will go ahead and change out the fuel pump as it looks easy and I will know there is at least one other new part. My hope is to settle this issue without dropping the tanks.

Do you know if I need vented caps or not? Still a bit fuzzy on this

 

Vented VS non vented depends on the type of tank you have. Non EVAP tanks only have the one small hose that leads to the fuel pump. These require a vented cap. EVAP tanks have a second small hose the runs to the charcoal canister. To work properly, these require a non vented cap.

I'm pretty sure that by 1979, all tanks had the EVAP setup.

Michael

 

The EFP (Electric Fuel Pump i think) should help on starts after sitting... especially if you let it run a few seconds before cranking. It will also help on hot re-starts when the fuel has boiled out of the carb bowl... again especially if you let it run a few seconds before crank.

As far as filters before the pump go, the OEM fuel pickup sock is enough for many pumps. Or a coarse mesh screen filter (eg 100 micron). Other pumps are more sensitive and need a finer filter. In general, filters on the suction side of the pump create restriction and may contribute towards vapor lock.

Today's gas blends are made for EFI. They boil easily. Many members, me included, have found a supplemental electric pump mounted low in the rear to be very helpful to maintain good starting and prevent vapor lock when running in hot weather.

 

Thanks... If I go back with EFP, would you recommend bypassing the MFP as noted before? I think that is my bottleneck.
I am going to try the MFP route if at all possible.
Good to know about the gas today.

 

Living in the Pacific Northwest, I've never suffered vapor lock that I know of but the electric pump should take care of it for those that do. I have had a carb ice up. Several times. That's a 'hole nother kettle of fish.

Since I've never installed an aftermarket electric, I have no actual experience with filter placement but based on the amount of junk I've scraped out of the fuel bowl on the Edelbrock on my truck, I'd still run a filter somewhere.

Michael

 

I press the gas pedal in once and turn the key, usually takes 2-3 times and then I let the engine choke and heat up. Once you press the gas pedal again it takes the choke off and if the engine isn't at optimal running temp ( 210 I believe ) it could sputter and die

 

My truck will spew gas if I fill it to close the neck and it's in the sun. I do love in Texas though. 115 temps sometimes

 

Effectiveness of the mechanical pump with today's gas seems to depend on environment, usage and the individual truck. Hot environment, hot re-start, long "off" periods, application and individual characteristics of certain trucks seem to benefit a lot with the electric pump.

No harm in trying to get it to work with the mechanical. That said, if you are fighting long crank times after the truck sits for a while or after hot soak, electric may help either as primary or auxiliary pump.

Good luck!

 

Since I have three trucks, they tend to sit a couple days between starts. If they sit too long, the fuel boils out of the carb and it's hard to start. In the 77, I regularly had to pop the hood and pour fuel down its neck.

I installed electric fuel pumps in all the trucks, and now they start as quick as EFI! Just turn the key, listen for the pump to build pressure, tap the accelerator and HIT IT! And you're off.

Don't try to push fuel through a mechanical fuel pump. If you blow the seal, the fuel floods into the crankcase. That's bad.

I installed the fuel pumps inside the frame rail, just ahead of the crossmember that holds the dual tank switching valve. I ran a clear filterbefore the pump to keep crap out of the pump. I run another up front, before the carb, so I can easily see what's going on.

Here's a link to the fuel pump install:
https://www.ford-trucks.com/forums/1...-the-79-a.html

 

Little update on Earl..... I have gotten used to running him every or every other day. I had a new issue today. We had 90+ degree heat today and when I went to start after sitting all day outside, it wouldn't without a little shot down the throat. Ran ok but a little rough. I had one stop on the way home and then it just quit like not getting any fuel at all. When I put a shot down the throat, it would run for just a few seconds... Im thinking vapor lock.
Now the configuration of fuel line is as follows... Hard line from the back to a soft hose (new) and it actually had a little downward loop in it routing up and to a fuel filter ( also new). New line to fuel pump. I was thinking that the fuel filter might be my bottle neck so I removed it and went direct route from hard line to the fuel filter. Put another shot down the throat and it ran perfectly.
My problem had to be in the filter or the loop that the line had made to get around to the pump. Now the question, is the filter sock in the tank sufficient or do I need a filter before the pump. There is not one between the pump and carb as I don't know how to plumb that in since it is hard line all the way. The truck ran fine with the mechanical pump so I really don't want the hassle of doing an electric unless completely necessary.

Thoughts.